CN110343278B - Composite polypropylene microporous membrane, preparation method thereof and lithium ion battery diaphragm comprising composite polypropylene microporous membrane - Google Patents
Composite polypropylene microporous membrane, preparation method thereof and lithium ion battery diaphragm comprising composite polypropylene microporous membrane Download PDFInfo
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/04—Coating
- C08J7/0427—Coating with only one layer of a composition containing a polymer binder
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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- C—CHEMISTRY; METALLURGY
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/10—Homopolymers or copolymers of propene
- C08J2323/12—Polypropene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2433/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
- C08J2433/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
- C08J2433/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
- C08J2433/10—Homopolymers or copolymers of methacrylic acid esters
- C08J2433/12—Homopolymers or copolymers of methyl methacrylate
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2483/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J2483/04—Polysiloxanes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a composite polypropylene microporous membrane, a preparation method thereof and a lithium ion battery diaphragm comprising the composite polypropylene microporous membrane. The method simplifies the production process of the composite polypropylene microporous membrane and improves the performance of the polypropylene microporous membrane. The composite polypropylene microporous membrane is used in a lithium ion battery diaphragm, and the non-polypropylene polymer porous layer is a polymer or a composition which can form gel with electrolyte, or a polymer with higher heat resistance than polypropylene, so that the cycle and safety performance of the lithium ion battery can be improved.
Description
Technical Field
The invention belongs to the technical field of microporous membranes, and particularly relates to a composite polypropylene microporous membrane, a preparation method thereof and a lithium ion battery diaphragm comprising the composite polypropylene microporous membrane.
Background
Polyolefin microporous membranes are polymeric membranes, which are porous membranes with pore sizes of 5nm to 1000nm, and are widely used in the fields of air-permeable materials (such as diapers, medical dressings, clothing liners, and the like), materials for liquid separation, ultrafiltration materials, membrane filtration materials, supercapacitor and battery separator materials, and the like.
The existing polyolefin microporous membrane preparation methods mainly comprise two methods, namely a melt extrusion stretching method (dry method) and a thermal induced phase separation method (TIPS, wet method). Wherein, the dry stretching process can be further divided into a unidirectional stretching process and a bidirectional stretching process. The wet preparation process includes adding high boiling point small molecular matter as pore creating agent into polyolefin and dissolving in organic solvent to form cast sheet, cooling to separate, extracting small molecules with organic solvent, and bi-directional stretching to form microporous structure. The dry biaxial stretching process is widely applied because a solvent is not required to be used, and the strength of the microporous membrane in the longitudinal and transverse directions is high.
The dry biaxial stretching process is mainly characterized in that a beta crystal form improver with a nucleating effect is added into polypropylene to form a polypropylene membrane with high beta crystal content, the beta crystal form is converted into alpha crystal form in the stretching process, and a microporous structure is formed by utilizing the difference of the densities of different phases of the polypropylene and is used for producing a single-layer polypropylene microporous membrane. In the prior research (CN1062357A), a microporous membrane obtained by stretching a polypropylene uniform original membrane with high beta-crystalline content is proposed, and the microporous membrane is prepared by adding a nucleating agent into a polypropylene resin for film formation by a melt processing method to obtain a membrane with beta-crystalline polypropylene. When the membrane prepared by the method is applied as a lithium ion battery diaphragm, the wettability of the carbonate polar electrolyte in the battery to the nonpolar polypropylene diaphragm is poor because polypropylene is a nonpolar material with low surface energy. Meanwhile, the non-polar polypropylene diaphragm and the battery pole piece are easy to be bonded poorly due to the difference of polarity in the battery assembling process. These factors all affect the capacity, cycling and performance of the battery. In addition, with the wide application of new energy vehicles and portable electric tools, high-power lithium ion batteries put higher requirements on the thermal stability of the diaphragm. Therefore, much research has been conducted on improving the cycle and use properties of batteries by modifying polyolefin microporous separators through surface graft polymerization or coating on the surfaces.
Disclosure of Invention
In order to solve the defects of the prior art, one of the objects of the present invention is to provide a composite polypropylene microporous membrane having a multi-layer membrane layer structure and a preparation method thereof.
The invention also provides a lithium ion battery diaphragm, which comprises the composite polypropylene microporous membrane; the lithium ion battery diaphragm comprising the composite polypropylene microporous membrane can form gel in electrolyte, so that the wettability of the electrolyte to the diaphragm is improved, and the heat resistance of the diaphragm is obviously improved.
The purpose of the invention is realized by the following technical scheme:
a composite polypropylene microporous membrane has a structure of at least two membrane layers, wherein the at least two membrane layers are at least one polypropylene microporous layer and at least one non-polypropylene polymer porous layer; the non-polypropylene polymer porous layer is a filler-containing non-polypropylene polymer porous layer.
According to the invention, the polypropylene microporous layer is prepared by stretching a polypropylene membrane containing a beta crystal form; the non-polypropylene polymer porous layer is prepared by stretching a non-polypropylene polymer film containing a filler.
In the present invention, the filler-containing non-polypropylene polymer is referred to as a non-polypropylene polymer porous layer because the filler and non-polypropylene polymer are broken at the interface thereof during stretching to form a porous structure.
According to the invention, the composite polypropylene microporous membrane has a two-layer membrane structure, wherein the membrane layer is a polypropylene microporous layer and a non-polypropylene polymer porous layer.
According to the invention, the composite polypropylene microporous membrane has a three-layer membrane layer structure, wherein the membrane layer is a polypropylene microporous layer and two non-polypropylene polymer porous layers; or the membrane layer comprises two polypropylene microporous layers and a non-polypropylene polymer porous layer.
According to the present invention, when the composite polypropylene microporous membrane comprises at least two polypropylene microporous layers, the at least two polypropylene microporous layers may be adjacent or non-adjacent.
According to the invention, when the composite polypropylene microporous membrane comprises at least two non-polypropylene polymer porous layers, the at least two non-polypropylene polymer porous layers are adjacent or not adjacent.
According to the present invention, when the composite polypropylene microporous membrane comprises at least two non-polypropylene polymer porous layers, the non-polypropylene polymers in the at least two non-polypropylene polymer porous layers are the same or different.
According to the present invention, when the composite polypropylene microporous membrane comprises at least two non-polypropylene polymer porous layers, the fillers in the at least two non-polypropylene polymer porous layers are the same or different.
According to the invention, the composite polypropylene microporous membrane has at least one of the following properties:
(1) the thickness of the composite polypropylene microporous membrane is 10-40 microns, preferably 15-20 microns;
(2) the air permeability Gurley value of the composite polypropylene microporous membrane is 100-400 s;
(3) the longitudinal tensile strength of the composite polypropylene microporous membrane is 100-200 MPa; the longitudinal elongation at break is 20-70%;
(4) the transverse tensile strength of the composite polypropylene microporous membrane is 25-50 MPa; the transverse elongation at break is 20-70%.
As described above, the polypropylene microporous layer is prepared by stretching a polypropylene membrane containing a beta-crystalline form; the polypropylene membrane containing the beta crystal form is stretched to form the alpha crystal form with a more stable crystal phase structure.
Wherein, the content of the beta-form in the polypropylene film containing the beta-form is more than or equal to 80 percent, preferably more than or equal to 85 percent.
Wherein the polypropylene microporous layer has a porosity of 40% or more, preferably 45% or more.
Wherein the polypropylene microporous layer has a thickness of 3 to 15 micrometers, preferably 5 to 10 micrometers.
The polypropylene microporous layer further comprises an interfacial compatilizer, and the interfacial compatilizer is selected from one or more of maleic anhydride grafted polypropylene, polyacrylic acid grafted polypropylene, glycidyl methacrylate grafted polypropylene, hydroxymethyl acrylamide grafted polypropylene, dibutyl maleate grafted polypropylene and the like. The addition of the interfacial compatilizer can improve the bonding performance between the polypropylene microporous layer and the non-polypropylene polymer porous layer, and the bonding between the polypropylene microporous layer and the non-polypropylene polymer porous layer is easier.
As described above, the non-polypropylene-based polymer porous layer is prepared by stretching a non-polypropylene-based polymer membrane sheet containing a filler.
The non-polypropylene polymer comprises but is not limited to one or more of polyethylene, polybutylene, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, polyethylene terephthalate, nylon, polyphenyl ether, polyether sulfone and polyether ketone.
The non-polypropylene polymer porous layer further comprises an interfacial compatilizer, and the interfacial compatilizer is selected from one or more of maleic anhydride grafted polypropylene, polyacrylic acid grafted polypropylene, glycidyl methacrylate grafted polypropylene, hydroxymethyl acrylamide grafted polypropylene, dibutyl maleate grafted polypropylene and the like. The addition of the interfacial compatilizer can improve the bonding performance between the non-polypropylene polymer porous layer and the polypropylene microporous layer, and the bonding between the non-polypropylene polymer porous layer and the polypropylene microporous layer is easier.
Wherein the filler is selected from at least one of inorganic filler or organic filler. The inorganic filler is selected from one or more of silicon dioxide, titanium dioxide, lanthanum oxide, zirconium dioxide, aluminum oxide, barium sulfate, calcium carbonate, carbon nitride, boehmite, silicon carbide, molecular sieve, talcum powder and montmorillonite.
Preferably, the inorganic filler is one or more of silica, alumina and boehmite.
Preferably, the inorganic filler is selected from the group consisting of the inorganic fillers mentioned above on a nano-scale.
The organic filler is selected from one or more of high temperature resistant polymers such as polytetrafluoroethylene, polyether ether ketone, polyether sulfone, polyphenyl ether and the like.
Preferably, the organic filler is selected from the above organic fillers in nanoscale.
Wherein the thickness of the non-polypropylene polymer porous layer is 3-15 microns, preferably 5-10 microns.
The invention also provides a preparation method of the composite polypropylene microporous membrane, which comprises the following steps:
(S1) adding a nucleating agent capable of promoting the formation of a beta crystal form into polypropylene, and uniformly mixing to obtain a polypropylene microporous layer to-be-extruded mixed system A;
(S2) adding a filler into the non-polypropylene polymer, and uniformly mixing to obtain a non-polypropylene polymer porous layer to-be-extruded mixed system B;
(S3) respectively melting and extruding the mixed system A of the step (S1) and the mixed system B of the step (S2), forming a melt comprising at least one polypropylene microporous layer and at least one non-polypropylene polymer porous layer structure through a multilayer co-extrusion die head, and then crystallizing and forming on a casting sheet roller to form a multilayer co-extruded membrane comprising at least one polypropylene microporous layer and at least one non-polypropylene polymer porous layer;
(S4) longitudinally stretching and transversely stretching the multilayer co-extruded membrane obtained in the step (S3) to obtain the composite polypropylene microporous membrane.
According to the present invention, in step S1, the polypropylene may be homo-polypropylene or co-polypropylene;
preferably, the polypropylene has an isotacticity of 90-98%; the melt index is 1-10g/10 min.
Preferably, the polypropylene has an isotacticity of 95-98%; the melt index is 2-5g/10 min.
According to the invention, in step S1, the nucleating agent capable of promoting the formation of the β -form is selected from nucleating agents having high nucleating efficiency and a β -form content of more than 50% under static crystallization conditions. Illustratively, the nucleating agent is selected from commercially available products or products synthesized according to methods known in the art.
According to the invention, the type of nucleating agent and the nucleating efficiency can be found in the literature Varga J. journal of macromolecular Science Physics 2002,41, 1121.
Illustratively, the nucleating agent may be either an organic small molecule such as N, N-dicyclohexyl terephthalamide, N-dicyclohexyl-2, 6 naphthalene diamide, γ -quinacridine, or the like, or an inorganic salt such as a hydrazine salt of adipic acid and/or suberic acid, a calcium salt of pimelic acid and/or suberic acid, a calcium salt or barium salt of tetrahydrophthalic anhydride, a calcium salt or barium salt of hexahydrophthalic anhydride, or the like; the nucleating agents can be mixed for use, and those skilled in the art can understand that the mixing ratio of the nucleating agents has no special requirement and is suitable for the system of the invention.
According to the invention, in step S1, the nucleating agent capable of promoting the formation of the beta-crystalline form is used in an amount of 0.001 to 0.1 wt% relative to the polypropylene.
According to the present invention, in step S1, an interfacial compatilizer may be further added to the mixed system a. The dosage ratio of the interfacial compatilizer to the polypropylene is 0-30 wt%.
According to the present invention, in step S2, the filler accounts for 20 to 70 wt% of the porous layer of the non-polypropylene based polymer.
Preferably, the organic filler comprises 10 to 60 wt% of the porous layer of the non-polypropylene based polymer; the inorganic filler accounts for 10 to 60 wt% of the porous layer of the non-polypropylene polymer.
According to the present invention, in step S2, an interfacial compatilizer may be further added to the mixed system B.
According to the present invention, in step S2, the interfacial compatibilizer is used in an amount of 0 to 30 wt% based on the non-polypropylene polymer.
According to the invention, in step S3, the melting temperature of the screw extruder extruding the polypropylene microporous layer is 200-260 ℃, preferably the melting temperature of the screw extruder extruding the polypropylene microporous layer is 220-250 ℃;
according to the present invention, in step S3, the melting temperature of the screw extruder for extruding the non-polypropylene polymer porous layer is 200 to 270 ℃, and preferably 220 to 250 ℃.
The multilayer co-extrusion die may be an adjustable die or a non-adjustable die according to the present invention, and those skilled in the art will recognize that it is suitable for use with the system of the present invention.
According to the invention, in step S3, the melt after multilayer co-extrusion is crystallized and formed on a casting sheet roller to obtain the composite film sheet. The temperature of the casting sheet roller is 110-140 ℃, and preferably the temperature of the casting sheet roller is 120-130 ℃.
According to the invention, in step S4, the temperature of the longitudinal stretching is 60-120 ℃, preferably the temperature of the longitudinal stretching is 80-110 ℃; the longitudinal stretching magnification is 2.5-5.5 times, preferably 3-5 times; the temperature of the transverse stretching is 120-150 ℃; preferably, the temperature of the transverse stretching is 130-140 ℃; the transverse stretching multiplying power is 2-5 times; preferably, the magnification of the transverse stretching is 2.5 to 4.5 times.
The invention also provides a lithium ion battery diaphragm which comprises the composite polypropylene microporous membrane.
The invention has the beneficial effects that:
the invention provides a composite polypropylene microporous membrane and a preparation method thereof, wherein in the preparation process of a biaxially oriented polypropylene membrane, a non-polypropylene porous layer is introduced by a melt co-extrusion method to form a membrane with at least two layers of structures, and the membrane is stretched in the longitudinal/transverse directions to realize the preparation of the composite polypropylene microporous membrane. The method simplifies the production process of the composite polypropylene microporous membrane and improves the performance of the polypropylene microporous membrane. The composite polypropylene microporous membrane is used in a lithium ion battery, and the non-polypropylene porous layer is a polymer or a composition which can form gel with electrolyte, or a polymer with higher heat resistance than polypropylene, so that the cycle and safety performance of the lithium ion battery can be improved.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be understood that various changes or modifications can be made by those skilled in the art after reading the description of the present invention, and such equivalents also fall within the scope of the invention.
Example 1
Uniformly mixing homopolymerized polypropylene resin with the melt index of 2.5g/10min and polypropylene beta-crystal nucleating agent N, N-dicyclohexyl-2, 6 naphthalene diamide which accounts for 0.03 wt% of the homopolymerized polypropylene resin, and melting at the temperature of 200-250 ℃ to form a polypropylene layer melt;
polyvinylidene fluoride and boehmite are uniformly mixed according to the mass ratio of 3:2, namely polyvinylidene fluoride accounting for 60 wt% of the total amount of the non-polypropylene layer and boehmite accounting for 40 wt% of the total amount of the non-polypropylene layer are uniformly mixed, and the mixture is melted at the temperature of 200 ℃ and 250 ℃ to form a non-polypropylene layer melt.
And (3) feeding the polypropylene layer melt and the non-polypropylene layer melt into a three-layer co-extrusion T-shaped die head through melt pipelines, wherein the polypropylene layer is arranged on two surfaces, the non-polypropylene layer is arranged on a core layer, and the polypropylene layer melt and the non-polypropylene layer melt are cooled and crystallized on a casting roll at the temperature of 130 ℃ to obtain the polypropylene membrane containing beta crystals. The film is longitudinally stretched by 4.5 times at 100 ℃, then enters a transverse stretching system, and is transversely stretched by 3.0 times at 135 ℃ to obtain the composite polypropylene microporous film with the thickness of 20 microns. Wherein the thickness of the two polypropylene microporous layers is 7 microns respectively, and the thickness of the core layer non-polypropylene porous layer is 6 microns.
When the prepared composite polypropylene microporous membrane is used as a lithium ion battery diaphragm, the wettability and the liquid absorption rate of the diaphragm to the lithium ion battery electrolyte are obviously improved compared with a single-layer polypropylene diaphragm.
Example 2
The same as in example 1, except that the composition of the polypropylene porous layer was different. The non-polypropylene layer is composed of polyvinylidene fluoride and polytetrafluoroethylene nano powder in a mass ratio of 4:1, namely polyvinylidene fluoride accounting for 80 wt% of the total amount of the non-polypropylene layer and polytetrafluoroethylene nano powder accounting for 20 wt% of the total amount of the non-polypropylene layer. The resulting composite microporous membrane had a thickness of 25 microns. Wherein the thickness of the two polypropylene microporous layers is respectively 8 microns, and the thickness of the core layer non-polypropylene porous layer is 9 microns.
When the prepared composite polypropylene microporous membrane is used as a lithium ion battery diaphragm, the wettability and the liquid absorption rate of the diaphragm to the lithium ion battery electrolyte are obviously improved compared with a single-layer polypropylene diaphragm.
Example 3
The procedure was the same as in example 1 except that the polypropylene layers were composed of polyethylene terephthalate (PET) and alumina in a mass ratio of 3:2, i.e., 60 wt% of polyethylene terephthalate to 40 wt% of alumina to the total amount of the non-polypropylene layers on both surfaces and the polypropylene layer outside the core layer. The resulting composite microporous membrane had a thickness of 25 microns. Wherein the thicknesses of the two non-polypropylene porous layers are respectively 8 microns, and the thickness of the polypropylene microporous layer of the core layer is 9 microns.
When the prepared composite polypropylene microporous membrane is used as a lithium ion battery diaphragm, the wettability and the liquid absorption rate of the diaphragm to the lithium ion battery electrolyte are obviously improved compared with a single-layer polypropylene diaphragm, and meanwhile, the heat resistance is also obviously improved.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (27)
1. The composite polypropylene microporous membrane is characterized by having a structure with at least two membrane layers, wherein the at least two membrane layers are at least one polypropylene microporous layer and at least one non-polypropylene polymer porous layer; the non-polypropylene polymer porous layer is a filler-containing non-polypropylene polymer porous layer;
the non-polypropylene polymer is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, polyethylene glycol terephthalate, nylon, polyphenyl ether, polyether sulfone and polyether ketone;
the filler is selected from at least one of inorganic filler or organic filler; when the filler is selected from inorganic fillers, the content of the filler accounts for 40 to 70 weight percent of the non-polypropylene polymer porous layer; when the filler is selected from organic fillers, the content of the filler accounts for 20-70 wt% of the non-polypropylene polymer porous layer;
the inorganic filler is selected from one or more of silicon dioxide, titanium dioxide, lanthanum oxide, zirconium dioxide, aluminum oxide, barium sulfate, calcium carbonate, carbon nitride, boehmite, silicon carbide, molecular sieve, talcum powder and montmorillonite; the organic filler is selected from one or more of the following high-temperature resistant polymers: polytetrafluoroethylene, polyetheretherketone, polyethersulfone, polyphenylene oxide;
the non-polypropylene polymer porous layer is prepared by longitudinally stretching and transversely stretching a non-polypropylene polymer film sheet containing a filler.
2. The composite polypropylene microporous membrane according to claim 1, wherein the composite polypropylene microporous membrane has a two-layer structure, wherein the two layers are the polypropylene microporous layer and the non-polypropylene polymer porous layer.
3. The composite polypropylene microporous membrane according to claim 1, wherein the composite polypropylene microporous membrane has a three-layer membrane layer structure, wherein the membrane layer is a polypropylene microporous layer and two non-polypropylene polymer porous layers; or the membrane layer comprises two polypropylene microporous layers and one non-polypropylene polymer porous layer.
4. The composite polypropylene microporous membrane according to claim 3, wherein when the composite polypropylene microporous membrane comprises at least two polypropylene microporous layers, the at least two polypropylene microporous layers may or may not be adjacent.
5. The composite polypropylene microporous membrane according to claim 3, wherein when the composite polypropylene microporous membrane comprises at least two non-polypropylene polymer porous layers, the at least two non-polypropylene polymer porous layers may or may not be adjacent.
6. The composite polypropylene microporous membrane according to claim 3, wherein when the composite polypropylene microporous membrane comprises at least two non-polypropylene polymer porous layers, the non-polypropylene polymers in the at least two non-polypropylene polymer porous layers are the same or different.
7. The composite polypropylene microporous membrane according to claim 3, wherein when the composite polypropylene microporous membrane comprises at least two non-polypropylene polymer porous layers, the filler in the at least two non-polypropylene polymer porous layers is the same or different.
8. The composite polypropylene microporous membrane according to any one of claims 1 to 7, wherein the composite polypropylene microporous membrane has at least one of the following properties:
(1) the thickness of the composite polypropylene microporous membrane is 10-40 microns;
(2) the air permeability Gurley value of the composite polypropylene microporous membrane is 100-400 s;
(3) the longitudinal tensile strength of the composite polypropylene microporous membrane is 100-200 MPa; the longitudinal elongation at break is 20-70%;
(4) the transverse tensile strength of the composite polypropylene microporous membrane is 25-50 MPa; the transverse elongation at break is 20-70%.
9. The composite polypropylene microporous membrane according to any one of claims 1 to 7, wherein the polypropylene microporous layer is prepared by stretching a polypropylene membrane containing a beta-crystalline form;
the content of the beta-crystal form in the polypropylene film containing the beta-crystal form is more than or equal to 80 percent.
10. The composite polypropylene microporous membrane according to claim 9, wherein the porosity of the polypropylene microporous layer is 40% or more;
the thickness of the polypropylene microporous layer is 3-15 microns.
11. The composite microporous polypropylene membrane of any one of claims 1 to 7, wherein the microporous polypropylene layer further comprises an interfacial compatibilizer, and the interfacial compatibilizer is one or more selected from the group consisting of maleic anhydride grafted polypropylene, polyacrylic acid grafted polypropylene, glycidyl methacrylate grafted polypropylene, hydroxymethyl acrylamide grafted polypropylene, and dibutyl maleate grafted polypropylene.
12. The composite polypropylene microporous membrane according to any one of claims 1 to 7, wherein the non-polypropylene polymer porous layer further comprises an interfacial compatibilizer, and the interfacial compatibilizer is one or more selected from maleic anhydride grafted polypropylene, polyacrylic acid grafted polypropylene, glycidyl methacrylate grafted polypropylene, hydroxymethyl acrylamide grafted polypropylene, and dibutyl maleate grafted polypropylene.
13. The composite polypropylene microporous membrane according to any one of claims 1 to 7, wherein the non-polypropylene based polymer porous layer has a thickness of 3 to 15 μm.
14. The method for preparing the composite polypropylene microporous membrane according to any one of claims 1 to 13, wherein the preparation method comprises the following steps:
(S1) adding a nucleating agent capable of promoting the formation of a beta crystal form into polypropylene, and uniformly mixing to obtain a polypropylene microporous layer to-be-extruded mixed system A;
(S2) adding a filler into the non-polypropylene polymer, and uniformly mixing to obtain a non-polypropylene polymer porous layer to-be-extruded mixed system B;
(S3) respectively melting and extruding the mixed system A of the step (S1) and the mixed system B of the step (S2), forming a melt comprising at least one polypropylene microporous layer and at least one non-polypropylene polymer porous layer structure through a multilayer co-extrusion die head, and then crystallizing and forming on a casting sheet roller to form a multilayer co-extruded membrane comprising at least one polypropylene microporous layer and at least one non-polypropylene polymer porous layer;
(S4) longitudinally stretching and transversely stretching the multilayer co-extruded membrane obtained in the step (S3) to obtain the composite polypropylene microporous membrane.
15. The method according to claim 14, wherein in step S1, the polypropylene is a homo-polypropylene or a co-polypropylene.
16. The method of claim 14, wherein the polypropylene has an isotacticity of 90-98%; the melt index is 1-10g/10 min.
17. The method according to claim 14, wherein in step S1, an interfacial compatibilizer is added to the mixed system a in an amount of 0 to 30 wt% based on the polypropylene.
18. The method according to claim 14, wherein in step S2, the organic filler accounts for 10 to 60 wt% of the porous layer of the non-polypropylene polymer; the inorganic filler accounts for 10 to 60 wt% of the porous layer of the non-polypropylene polymer.
19. The method according to claim 14, wherein in step S2, an interfacial compatibilizer is added to the mixed system B in an amount of 0 to 30 wt% based on the non-polypropylene polymer.
20. The production method according to any one of claims 14 to 19, wherein in step S3, a melting temperature of a screw extruder for extruding the polypropylene microporous layer is 200 to 260 ℃.
21. The method according to claim 20, wherein the melting temperature of the screw extruder extruding the microporous polypropylene layer is 220 to 250 ℃.
22. The production method according to any one of claims 14 to 19, wherein in step S3, the melting temperature of the screw extruder for extruding the non-polypropylene-based polymer porous layer is 200 to 270 ℃.
23. The method according to claim 22, wherein in step S3, the melting temperature of the screw extruder for extruding the porous layer of the non-polypropylene polymer is 220 to 250 ℃.
24. The method as claimed in any one of claims 14 to 19, wherein in step S3, the melt after the multilayer co-extrusion is crystallized and formed on a casting sheet roller at a temperature of 110-140 ℃ to obtain the composite film.
25. The production method according to any one of claims 14 to 19, wherein in step S4, the temperature of the longitudinal stretching is 60 to 120 ℃, and the magnification of the longitudinal stretching is 2.5 to 5.5 times; the temperature of the transverse stretching is 120-150 ℃, and the magnification of the transverse stretching is 2-5 times.
26. The method as claimed in claim 25, wherein the temperature of the longitudinal stretching is 80-110 ℃, the magnification of the longitudinal stretching is 3-5 times, the temperature of the transverse stretching is 130-140 ℃, and the magnification of the transverse stretching is 2.5-4.5 times.
27. A lithium ion battery separator, wherein the lithium ion battery separator comprises the composite polypropylene microporous membrane according to any one of claims 1 to 13.
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| CN110931691B (en) * | 2019-11-14 | 2022-05-13 | 珠海格力绿色再生资源有限公司 | Diaphragm for lithium ion battery, preparation method of diaphragm and lithium ion battery containing diaphragm |
| CN111592717B (en) * | 2020-05-28 | 2022-05-13 | 四川大学 | Polypropylene microporous membrane containing polytetrafluoroethylene modifier and preparation method thereof |
| CN111816822B (en) * | 2020-06-18 | 2022-03-01 | 中国科学院化学研究所 | Functional lithium-supplementing diaphragm and preparation method thereof |
| CN111883724B (en) * | 2020-08-06 | 2022-09-02 | 深圳市星源材质科技股份有限公司 | Multilayer polypropylene microporous membrane and preparation method and application thereof |
| CN116063773A (en) * | 2021-10-29 | 2023-05-05 | 中国石油化工股份有限公司 | Polypropylene composition, preparation method and application thereof, and polyolefin microporous breathable film |
| CN114566758B (en) * | 2021-12-29 | 2024-03-29 | 武汉中兴创新材料技术有限公司 | Film, preparation method thereof and battery comprising film |
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